The long-term goal of this project is to understand the molecular basis of corneal epithelial differentiation. To accomplish this goal, a combination of cell culture, monoclonal antibody and recombinant DNA techniques will be used to study three separate but closely related projects. 1. To study the mechanisms underlying the differential expression of keratin proteins in rabbit corneal epithelium by: (a) Determining whether the synthesis of the 48K/56K hyperproliferation-related keratin pair is regulated translationally; (b) Isolating and characterizing appropriate cDNA probes for the 48K/56K and the 55K/64K corneal differentiation keratins; (c) Using these cDNA probes to study transcriptional and post-transcriptional regulation of keratin synthesis; and (d) Isolating the genes of 55K/64K rabbit corneal epithelial keratins to study the mechanism of their tissue-specificity and "paired" coexpression. 2. To study the possible role of basement membrane (BM) heterogeneity in regulating keratin expression in corneal epithelium by: (a) Generating a panel of monoclonal antibodies whose heterogeneous staining with corneal and limbal BM correlates with the basal expression of 64K keratin; and (b) Studying the structure and possible function of these novel basement membrane components. 3. To study the transdifferentiation of conjunctival to corneal epithelium by: (a) Asking whether adult or embryonic conjunctival epithelium can be induced by corneal stroma to become a bona fide corneal epithelium as defined by the expression of the 64K corneal keratin; and (b) Comparing the behavior of corneal and conjunctival epithelial cells under identical cell culture conditions.